An engine combusts a mixture of air and fuel within cylinders to drive pistons that rotatably turn a crankshaft to generate drive torque. Exhaust gas resulting from combustion is expelled from the cylinders into an exhaust system. The exhaust system includes exhaust treatment components to decrease emissions. One example exhaust treatment component for engines is a selective catalytic reduction (SCR) system. SCR systems inject a reductant, e.g., urea solution, into the exhaust system upstream from an SCR catalyst. The mixture of the reductant and the exhaust gas reacts with the SCR catalyst, thereby decreasing emissions, such as nitrogen oxides (NOx). The temperature of the reductant injector varies during operation, which affects the durability of the reductant injector and/or the spray quality of the reductant injected by the reductant injector if not accounted for. Moreover, at high temperatures, the reductant injector could inject an incorrect amount of reductant into the exhaust system. Conventional temperature models do not accurately model the temperature of the reductant injector. Thus, while these systems work for their intended purpose, there remains a need for improvement in the relevant art.